Cannot start Docker

A thought, I had been in the process of restoring a backup to this installation, but became unstuck. Perhaps this has something to do with the latest inability to load openemr in the browser? I had been following the instructions here, but the command
docker exec -it $(docker ps | grep _openemr | cut -f 1 -d " ") /bin/sh
(step 9) produces this error:

robert@roberts-Lenovo-B590:~/Downloads$ docker exec -it $(docker ps | grep _openemr | cut -f 1 -d " ") /bin/sh
"docker exec" requires at least 2 arguments.
See 'docker exec --help'.

Usage:  docker exec [OPTIONS] CONTAINER COMMAND [ARG...]

Run a command in a running container